hakorune/docs/development/current/main/PHASE_74_SUMMARY.md

Phase 74: BindingId Infrastructure - Implementation Summary

Date: 2025-12-13 Status: ✅ Complete Test Results: All acceptance criteria met

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Implementation Deliverables

Files Created

1. src/mir/binding_id.rs (130 lines)

   • BindingId type definition
   • Overflow protection with debug_assert!
   • 5 unit tests (creation, next, display, ordering, overflow)

2. docs/development/current/main/phase74-bindingid-infrastructure.md (~300 lines)

   • Complete architecture documentation
   • Implementation details
   • Test strategy
   • Migration roadmap (Phase 75-77)

Files Modified

1. src/mir/mod.rs (+2 lines)

   • Added pub mod binding_id;
   • Re-exported BindingId in public API

2. src/mir/builder.rs (+85 lines)

   • Added next_binding_id: u32 field
   • Added binding_map: BTreeMap<String, BindingId> field
   • Implemented allocate_binding_id() method
   • Added 4 unit tests (initialization, sequential, shadowing, parallel)

3. src/mir/builder/vars/lexical_scope.rs (+30 lines)

   • Extended LexicalScopeFrame with restore_binding field
   • Modified pop_lexical_scope() to restore BindingId mappings
   • Modified declare_local_in_current_scope() to allocate BindingIds

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Test Results

Unit Tests (9 total)

src/mir/binding_id.rs:
  ✅ test_binding_id_creation
  ✅ test_binding_id_next
  ✅ test_binding_id_display
  ✅ test_binding_id_ordering
  ✅ test_binding_id_overflow (debug only)

src/mir/builder.rs:
  ✅ test_binding_map_initialization
  ✅ test_binding_allocation_sequential
  ✅ test_shadowing_binding_restore
  ✅ test_valueid_binding_parallel_allocation

Regression Tests

cargo test --release --lib:     958 passed ✅
cargo test --features normalized_dev --test normalized_joinir_min:  54 passed ✅
cargo build --lib:              Success ✅

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Key Design Decisions

1. Parallel Allocation

• ValueId and BindingId allocate independently
• next_value_id() → value_gen.next()
• allocate_binding_id() → next_binding_id++

2. BTreeMap for Determinism

• binding_map: BTreeMap<String, BindingId> (not HashMap)
• Consistent with Phase 25.1 determinism strategy

3. Symmetric Restoration

• pop_lexical_scope() restores both variable_map and binding_map
• Prevents asymmetric bugs

4. Overflow Protection

• debug_assert! in allocate_binding_id() and BindingId::next()
• Test only runs in debug builds (#[cfg(debug_assertions)])

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What's Next: Phase 75

Pilot Integration Plan

1. Identify 1-2 files for isolated BindingId usage
2. Add logging (e.g., NYASH_BINDING_TRACE=1)
3. Validate behavior unchanged via smoke tests
4. Document findings for Phase 76 promotion

Candidate Components

• src/mir/builder/vars/ - Local variable tracking
• src/mir/builder/stmts.rs - Statement lowering (shadowing-heavy)

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Acceptance Criteria Status

Criterion	Status	Notes
cargo build --lib succeeds	✅	No compilation errors
cargo test --release --lib all pass	✅	958 tests passed
cargo test --features normalized_dev --test normalized_joinir_min passes	✅	54 tests passed
New unit tests pass	✅	9 tests added, all passing
Zero production impact	✅	Infrastructure-only, no behavior changes

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Conclusion

Phase 74 successfully establishes the BindingId infrastructure with:

• ✅ Complete implementation (4 files, 547 lines)
• ✅ Full test coverage (9 unit tests + existing smoke tests)
• ✅ Zero regressions (958 + 54 tests pass)
• ✅ Production-ready (no behavior changes)

Ready for Phase 75 pilot integration.